This invention relates to a method and apparatus for radiolabeling red blood cells.
Radioscanning and similar radiographic techniques are used increasingly in biological medical research and diagnostic procedures. Radioscanning procedures involve the preparation of radioactive media which, upon injection, infusions or otherwise introduced into a biological subject, become localized in specific organs, tissue or skeletal material or remain in the blood stream which are under study. Traces, plots or so-called "photographs" of the distribution of the radioactive material may be made by various radioscanning means, such as radiodetection rays, traversing scanner, scintillation cameras or the like. The resultant distribution in corresponding relative intensity would then be used to indicate the presence of aberrations, pathological conditions or the like.
Technetium-99m (Tc-99m) recently has gained wide acceptance as a tagging moiety. The value of technetium-99m for clinical scintiscanning stems both from its physical and from its chemical properties. Its short half-life, of 6 hours, coupled with an absence of primary .beta.-emission, result in very low radiation doses to tissues. The high activities can therefore be administered in as short a time required for a scan and enables several views of the area of the body being examined. The low energy of the gamma-emission, 140 KeV enables a picture to be obtained with a focusing collimator, of virtually a surface layer a few cm in thickness. This is due partly to improved resolution and partly to reduction in the contribution of radiation from deeper structures by self-absorption.
Prior to the present invention, red blood cells have been labeled with technetium-99m in order to provide visualization of the blood pools and the spleen in a patient. Labeling methods include both in vitro techniques and in vivo techniques. The in vitro techniques are undesirable since they are cumbersome and time-consuming. The in vivo techniques generally utilized comprise the sequential injection of stannous pyrophosphate followed by injection of technetium-99m as pertechnetate approximately 30 minutes later. Unfortunately, the procedure results in relatively incomplete radiolabeling of red blood cells and results in gastric visualization in some patients that causes undesirable background which reduces visualization of the blood.
Accordingly, it would be desirable to provide a means for labeling red blood cells which minimizes gastric visualization and improves the efficiency of labeling as compared to the efficiency of present methods for labeling red blood cells. Furthermore, it would be desirable to provide such a means which eliminates the cumbersome manipulation procedures required in presently employed in vivo processes for labeling red blood cells.